Devices and methods for cervical lateral fixation

ABSTRACT

Devices and methods are provided for treatment of the cervical spine. The devices and methods allow for treatment to be delivered from a lateral or posterior-lateral location of a subject, proximate to the cervical region of the spine. One exemplary embodiment of a spinal implant includes an elongate cage member and a plate member appended to a proximal end of the cage member. The plate member can be oriented in a manner such that it is asymmetric with respect to a long axis of the cage member. In another exemplary embodiment, an implant includes a cage member having a distal end that has an asymmetrical, bulleted shape such that the distal end is biased towards a superior or cranial direction. In a third exemplary embodiment, an implant includes a spinal fixation element and at least two mounting eyelets formed thereon. Exemplary methods related to implanting spinal implants from a lateral or posterior-lateral location are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/222,776 filed on Aug. 31, 2011, and entitled “DEVICES AND METHODS FORCERVICAL LATERAL FIXATION,” which is incorporated by reference herein inits entirety.

FIELD

The present disclosure relates to devices and methods for treating thecervical region of the spine, and more particularly relates to devicesfor and methods of performing treatments to that region from a lateralor posterior-lateral location of a subject.

BACKGROUND

The human spine includes vertebrae and joints that work together toprotect the spinal cord from injury during motion and activity. Thespinal cord generally includes nerve elements that travel from the brainto other portions of the body so that the brain can command the otherportions of the body to respond in particular manners based onbioelectrical and biochemical signals transmitted by the brain, throughthe spinal cord, and ultimately to the portion of the body beingcommanded by the brain.

The spine itself is typically grouped into three sections: the cervicalspine (which is in the region of the neck), the thoracic spine (which isin the region of the middle of the back), and the lumbar spine (which isin the region of the lower back). The cervical spine, which is typicallyconsidered to include the C1-C7 vertebrae, is known as a sensitive areaof the spine that requires caution when performing surgical proceduresin the area. The bones in this area are small and delicate. Surgicalprocedures performed in that area can include procedures for treatingspinal stenosis and nerve root compression. Procedures performed in thecervical region of the spine have typically involved approaching theregion from an anterior location of a subject, and care must be taken toavoid damage to the spinal cord or other anatomical structures locatedin that vicinity, such as the Carotid artery and the Jugular vein.

It would be desirable to provide devices and methods that can be usedfor treatment of the cervical region of the spine from locations thatare considered lateral or posterior-lateral of a subject while stillallowing appropriate care to be taken to avoid damage to anatomicalstructures in that region.

SUMMARY

Devices and methods are generally provided for treatment of the cervicalspine from a lateral or posterior-lateral location of a subject. In oneembodiment a spinal implant includes an elongate cage member having adistal insertion end and a proximal anchoring end and a plate memberappended to the cage member in proximity to the proximal anchoring end.The cage member can be oriented in a first direction. An externalsurface of the cage member extends between the proximal and distal endsof the cage member, which can be defined by a superior surface, aninferior surface, an anterior wall, and a posterior wall. The cagemember can have a hollow interior and a plurality of openings formed inthe external surface. The plate member can have a long axis that isgenerally perpendicular to the first direction of the cage member. Theplate member can have a curve along a short axis of the plate member,and the plate member can be asymmetric with respect to the long axis ofthe cage member. For example, the plate member can be oriented withrespect to the elongate cage member such that a midpoint of the platemember is disposed anterior to the long axis of the cage member.

In one embodiment the superior surface of the cage member is generallyconcave while the inferior surface of the cage member is generallyconvex. The distal insertion end of the cage member can have anasymmetrical, bulleted shape. Such a shape can result from a curve ofthe inferior surface being greater than a curve of the superior surface,and, as a result, the distal insertion end is biased toward a superiordirection. The posterior and anterior walls of the cage member can alsoinclude a curve. The posterior wall can have a curve that is generallyconcave; the anterior wall can have a curve that is generally convex. Inone embodiment a radius of the curve of the anterior wall of the cagemember can be substantially the same as a radius of the curve of theshort axis of the plate member.

The cage member can be configured to be delivered to a cervical spinethrough a lateral surgical approach. Additionally, the superior and/orinferior surfaces of the cage member can include one or more surfacefeatures that are configured to prevent migration of the implant. Theplate member can include a plurality of wings. The wings can beconfigured to engage a surface by way of attachment features. In oneembodiment an angle formed between the short axis of the plate memberand the plane of the cage member is less than 90 degrees. For example,the angle between the short axis and the cage member plane can be in therange of about 35 degrees to about 80 degrees. The implant itself caninclude one or more bores configured to receive a screw to aid insecuring the implant to bone.

In another exemplary embodiment of a spinal implant, the implantincludes an elongate cage member having distal and proximal ends, thedistal end having an asymmetrical, bulleted shape. The shape is suchthat a curve of an inferior surface of the cage member is greater than acurve of a superior surface of the cage member. As a result, the distalend is biased towards a superior direction. An external surface of thecage member extends between the ends of the cage member and is definedby the aforementioned superior surface, which is generally concave, andthe aforementioned inferior surface, which is generally convex, as wellas an anterior wall and a posterior wall. The cage member can have ahollow interior and a plurality of openings formed in its externalsurface.

In one embodiment the cage member can also include a plate member thatis integrally formed on the cage member in proximity to the proximal endof the cage member. The plate member can have a long axis that isgenerally perpendicular to a long axis of the cage member. The platemember can also have a curve along a short axis of the plate member. Inone embodiment the plate member can be asymmetric with respect to thelong axis of the cage member. In another embodiment the plate member canbe oriented with respect to the cage member such that a midpoint of theplate member is disposed anterior to the long axis of the cage member.In still another embodiment an angle formed between the short axis ofthe plate member and the long axis of the cage member is less than 90degrees. For example, the angle between the two axes can be in the rangeof about 35 degrees to about 80 degrees.

The cage member can be configured to be laterally delivered to acervical spine. Additionally, the superior and/or inferior surface ofthe cage member can include one or more surface features configured toprevent migration of the implant. The posterior and anterior walls ofthe cage member can include a curve. The posterior wall can have a curvethat is generally concave; the anterior wall can have a curve that isgenerally convex. In one embodiment a radius of the curve of theanterior wall of the cage member can be substantially the same as aradius of the curve of the short axis of the plate member. The implantitself can include one or more bores configured to receive an anchormember, such as a screw, to aid in securing the implant to bone.

In one exemplary embodiment of a method for treating a cervical spine,the method includes inserting a spinal implant between two adjacentvertebrae of a cervical spine and fixing a plate member of the spinalimplant such that a midpoint of the plate member is disposed anterior toa long axis of the spinal implant. The insertion of the implant canoccur from a position that is lateral or posterior-lateral to thecervical spine. For example, in one instance, insertion can occuranywhere between a position that is substantially perpendicular to aplane extending through a subject that substantially bisects the subjectinto two substantially equal halves and a position that is substantially45 degrees in a posterior-direction to the plane. The spinal implant caninclude a cage member. The plate member can be fixed relative to thecage member. In one embodiment the plate member can be oriented withrespect to the cage member such that a midpoint of the plate member isdisposed anterior to a long axis of the cage member.

In another exemplary embodiment of an implantable spinal fixationdevice, the device can include an elongate rod member and at least twomounting eyelets. The first mounting eyelet can be formed on theelongate rod member in proximity to a distal end of the rod member. Thesecond mounting eyelet can also be formed on the elongate rod member,remote from the first mounting eyelet. An opening can be formed in eachof the first and second mounting eyelets. The first mounting eyelet canhave a central axis that intersects a longitudinal axis of the rodmember or a central axis that is offset from a longitudinal axis of therod member. Likewise, the second mounting eyelet can have a central axisthat intersects a longitudinal axis of the rod member or a central axisthat is offset from a longitudinal axis of the rod member. Thus, in oneembodiment both a central axis of the first mounting eyelet and acentral axis of the second mounting eyelet can intersect a longitudinalaxis of the rod member. In another embodiment a central axis of thefirst mounting eyelet can intersect a longitudinal axis of the rodmember while a central axis of the second mounting eyelet can be offsetfrom the longitudinal axis of the rod member. In still anotherembodiment both a central axis of the first mounting eyelet and acentral axis of the second mounting eyelet can be offset from thelongitudinal axis of the rod member.

The mounting eyelets can have a variety of locations with respect toeach other and with respect to proximal and distal ends of the rodmember. For example, the second mounting eyelet can be in proximity to aproximal end of the rod member. By way of further example, the firstmounting eyelet can be at the distal end of the elongate rod member. Alength of the elongate rod member can be adjustable between the firstand second mounting eyelets. In one embodiment a first segment of theelongate rod member can be configured to slide with respect to a secondsegment of the elongate rod member. A diameter of the second segment canbe larger than a diameter of the first segment and the second segmentcan be configured to slidingly receive the second segment. In anotherembodiment the elongate rod member can include one or more lockingmembers disposed between first and second segments of the elongate rodmember. The one or more locking members can be configured to selectivelymove and lock the segments to adjust a length of the elongate rod memberbetween the first and second mounting eyelets.

The rod member can have a pre-determined curve, and in one embodimentthe curve can be complementary of a curve of a spine. Alternatively, therod member can be substantially thin and flat. The rod member can alsobe bendable. In one embodiment the rod member can include a plurality ofvertices disposed between the first and second mounting eyelets. Forexample, a first vertex can be disposed on one side of a longitudinalaxis of the rod member and a second vertex can be disposed on anopposite side of the longitudinal axis of the rod member. The openingsof the first and second mounting eyelets can be configured to receive ascrew therein such that a central axis disposed through a screw receivedby the first mounting eyelet is in a non-parallel position with respectto a central axis disposed through a screw received by the secondmounting eyelet.

In another exemplary embodiment of a method for treating a cervicalspine, the method includes inserting a rod member having first andsecond mounting eyelets through an opening proximate to a cervicalspine, attaching the first mounting eyelet to a first vertebra in acervical spine, and attaching a second mounting eyelet to a secondvertebra in a cervical spine. The opening can be located lateral orposterior-lateral to the cervical spine. Either or both of the mountingeyelets can be offset from a longitudinal axis of the rod member. In oneembodiment the method can include adjusting a length of the rod memberbetween the first and second mounting eyelets. The method can alsoinclude adjusting a shape of the rod member between the first and secondmounting eyelets. Further, a second rod member can be inserted throughthe opening that is proximate to the cervical spine. The second rodmember can be positioned such that the second rod member issubstantially parallel to the first rod member. The second rod membercan then be attached to vertebrae in the cervical spine, for instance byattaching a first mounting eyelet of the second rod member to onevertebra and attaching a second mounting eyelet of the second rod memberto another vertebra.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic view of a human subject illustrating an exemplarylocation for an incision in which implants of the nature disclosedherein can be inserted into the subject;

FIG. 2A is a perspective view of an anterior and superior portion of oneexemplary embodiment of a spinal implant that includes a cage member anda plate member;

FIG. 2B is a perspective view of a posterior and superior portion of thespinal implant of FIG. 2A;

FIG. 2C is a perspective view of a posterior portion of the spinalimplant of FIG. 2A;

FIG. 2D is a perspective view of a proximal end of the spinal implant ofFIG. 2A;

FIG. 2E is a perspective view of an anterior portion of the spinalimplant of FIG. 2A;

FIG. 2F is a perspective view of an inferior portion of the spinalimplant of FIG. 2A;

FIG. 3A is an anterior view of one exemplary embodiment of a spinalimplant that includes a cage member, the implant being disposed betweentwo adjacent vertebrae;

FIG. 3B is a top view of another exemplary embodiment of a spinalimplant that includes a cage member and a plate member;

FIG. 4A is a top view of an exemplary embodiment of a spinal implantthat includes a bend zone between a cage member and a plate member, andhaving a vertebral body disposed therebelow;

FIG. 4B is a top view of another exemplary embodiment of a spinalimplant that includes multiple bend zones between a cage member and aplate member;

FIG. 4C is a top view of yet another exemplary embodiment of a spinalimplant in which the plate member appended to the cage member issubstantially flat;

FIG. 4D is a top view of still another exemplary embodiment of a spinalimplant in which the plate member appended to the cage member isgenerally V-shaped;

FIG. 4E is a top view of another exemplary embodiment of a spinalimplant in which the plate member appended to the cage member isgenerally U-shaped;

FIG. 4F is a top view of yet another exemplary embodiment of a spinalimplant in which the plate member appended to the age member isgenerally U-shaped and in which bend zones are located between the cagemember and the plate member;

FIG. 5A is an anterior view of an exemplary embodiment of plate memberof a spinal implant;

FIG. 5B is a top schematic view of an exemplary embodiment of a fixationelement being disposed in a spinal implant;

FIG. 6A is a distal perspective view of another exemplary embodiment ofa spinal implant that is threaded and includes a tapered distal end;

FIG. 6B is a proximal perspective view of the spinal implant of FIG. 4A;

FIG. 6C is a proximal view of the spinal implant of FIG. 4A;

FIG. 7 is a distal perspective view of an exemplary embodiment of aspinal implant that is threaded and has a non-tapered distal end;

FIG. 8 is a perspective view of another exemplary embodiment of a spinalimplant that includes a plurality of edges and spikes disposed around acircumference thereof;

FIG. 9 is a perspective view of yet another exemplary embodiment of aspinal implant that includes a plurality of spikes disposed around acircumference thereof;

FIG. 10 is a perspective view of still another exemplary embodiment of aspinal implant that is threaded and includes a plurality of fingers;

FIG. 11A is a schematic view of an exemplary embodiment of a spinalimplant that includes a plurality of edges disposed around acircumference thereof before it is disposed between two vertebrae;

FIG. 11B is a schematic view of the spinal implant of FIG. 9A after itis disposed between two vertebrae;

FIG. 12A is a schematic view of another embodiment of a spinal implantthat is threaded and is disposed between two vertebrae;

FIG. 12B is a detail view of the spinal implant of FIG. 10A;

FIG. 13A is a perspective view of an exemplary embodiment of a spinalimplant that includes lateral staples and is attached to a cervicalregion of a spine;

FIG. 13B is a perspective view of a lateral staple for use implantationin a cervical region of a spine;

FIG. 14A is a perspective view of one exemplary embodiment of a spinalimplant that includes a rod member having mounting eyelets;

FIG. 14B is a perspective view of the two spinal implants of FIG. 12Aattached to a cervical region of a spine;

FIG. 15 is a schematic view of another exemplary embodiment of a spinalimplant having a substantially S-shape;

FIG. 16A is a perspective view of another exemplary embodiment of aspinal implant having a rod member coupled to a fixation element by wayof a connector;

FIG. 16B is a detail view of a mounting eyelet of the spinal implant ofFIG. 13A;

FIG. 17A is a perspective view of still another exemplary embodiment ofa spinal implant having a telescoping rod member and that is attached toa cervical region of a spine;

FIG. 17B is a perspective view of the spinal implant of FIG. 15A;

FIG. 18A is a perspective view of an exemplary embodiment of a spinalimplant having a locking mechanism disposed between two segments of arod member and being attached to a cervical region of a spine;

FIG. 18B is a perspective view of the spinal implant of FIG. 16A fromthe posterior side;

FIG. 18C is a perspective view of the spinal implant of FIG. 16A from alateral side;

FIG. 19 is a perspective view of another exemplary embodiment of aspinal implant having three mounting eyelets and being attached to acervical region of a spine;

FIG. 20 is a perspective view of yet another exemplary embodiment of aspinal implant that is generally thin and flat and is attached to acervical region of a spine;

FIG. 21A is a perspective view of still another exemplary embodiment ofa spinal implant having a plurality of bends in its shape and that isattached to a cervical region of a spine; and

FIG. 21B is a perspective view of the spinal implant of FIG. 19A.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Devices and methods for fixing and/or stabilizing a location of bones inthe cervical region of the spine are generally provided. The fixationapproach disclosed herein allows for delivery of spinal implants in amanner not typically relied upon for spinal fixation procedures. Inparticular, as illustrated in FIG. 1, the devices and methods allow forspinal implants to be implanted in a subject H from a lateral point ofaccess LP. Implants can be inserted through the lateral point of accessat an angle that is substantially perpendicular to a sagittal plane S.Alternatively, implants can be inserted from a posterior-laterallocation. For example, a point of access can be disposed in a directionthat is posterior of the lateral point of access LP. By way of furtherexample, an angle of insertion defined by a plane I can benon-perpendicular to the sagittal plane S, preferably at an angle thatis posterior to a plane P that is substantially perpendicular to thesagittal plane S. As shown, in one exemplary embodiment an angle A₁formed between the plane P and the insertion plane I is approximately 45degrees in a posterior-direction to the plane P. The angle of insertionA₁ can occur at any access point, including the lateral point of accessLP as shown, or at a point of access that is posterior to the lateralpoint of access LP. The lateral or posterior-lateral approach can beachieved in view of the present devices and methods without creating asubstantial risk of causing undesirable damage to this sensitive area,which contains anatomical structures including the Carotid artery andJugular vein.

A variety of devices and methods are disclosed herein. Some devicesinclude spinal implants configured to be disposed between adjacentvertebrae. Other devices include spinal fixation elements that can beconfigured to extend from one vertebra to one or more additionalvertebrae, even if those vertebrae are not adjacent. The methods includesurgical techniques that allow implants to be disposed through a smallincision that is positioned lateral or posterior-lateral of a subjectbeing treated. In the present disclosure, like-numbered components ofthe embodiments generally have similar features, and thus within aparticular embodiment each feature of each like-numbered component isnot necessarily fully elaborated upon. Further, to the extent thatlinear or circular dimensions are used in the description of thedisclosed devices and methods, such dimensions are not intended to limitthe types of shapes that can be used in conjunction with such devicesand methods. A person skilled in the art will recognize that anequivalent to such linear and circular dimensions can easily bedetermined for any geometric shape. Sizes and shapes of each of devices,and the components thereof, can depend at least on the anatomy of thesubject in which the devices will be used and the size and shape ofcomponents with which the devices will be used.

Lateral Anterior Fusion Cage

FIGS. 2A-2F illustrate one exemplary embodiment of a spinal implant 10,which is in the form of a lateral anterior fusion cage 20. As explainedbelow, the disclosed lateral anterior fusion cage has a design thatlends itself to implantation in a subject's spine via a lateral orposterior-lateral surgical approach. Moreover, the design is such thatthe implant maximizes the footprint of the implant component that is toreside between adjacent vertebral bodies while providing a largeinternal volume, which can serve as a graft chamber. As described below,the implant is asymmetric about a long axis of its cage. For example, aplate member 50 is asymmetric about a long axis L₁ of the cage member 20such that the plate member is not equally sized and shaped on both sidesof the long axis L₁. In one illustrated embodiment, the plate member 50is entirely on one side of the long axis L₁.

In the description of the lateral anterior fusion cage that follows,reference is made to orientation of the device when in a condition inwhich it is implanted within a subject. That is, with the cage member 20disposed between adjacent vertebral bodies and the plate member (ifpresent) attached to a lateral wall of the vertebral bodies. In oneexemplary embodiment the cage member can closely match an anatomy of acentral to posterior portion of a vertebral body and can therefore bedisposed in the central to posterior portion of the cervical region ofthe spine.

As illustrated, the implant 10 can include both an elongate cage member20 that is configured to be inserted between adjacent vertebrae and anoptional plate member 50 that can be appended to the cage member 20 andthat can be used to assist in securing the implant 10 at a desiredlocation, such as on a lateral wall of one or more vertebral bodies. Thecage member 20 is generally oriented in a transverse plane of the bodywhen implanted, extending laterally to medially between its proximal anddistal ends 20 p, 20 d. The appended plate member 50, when implanted,generally extends in the caudal to cephalad direction. The cage membercan be regarded to be of a generally rectangular shape in that it iselongate and has four sides. However, as explained below, each of thesides can be non-linear in shape. As a result, in some embodiments, thecage member 20 can be described as having a generally banana-like orcanoe-like shape.

As shown in FIGS. 2A and 2F, the cage member 20 can be elongate, and forreference purposes can be described as being oriented along alongitudinal axis L₁ in the transverse plane. The cage member 20 canalso be described as having an external surface that extends between theproximal and distal ends 20 p, 20 d, which is defined by a superiorsurface 22, an inferior surface 24, an anterior wall 26, and a posteriorwall 28. One or more relief slits or openings 30 can be formed in theexternal surface to, optionally, permit bone graft and/or bonegrowth-promoting material to be disposed therein, and thus facilitateintegration of the implant within a subject.

The distal end 20 d of the cage member 20 can be configured forinsertion between vertebral bodies of a subject and to optimize stablefixation within the subject. As shown, the distal end 20 d is of arounded or bullet-shaped nature. Generally, the distal end 20 d servesas the leading edge of the implant 10 when disposing the implant 10through an incision and into an intervertebral implantation site. Theproximal end 20 p of the cage member 20, on the other hand, is thetrailing end of the spinal implant 10 and can include features adaptedfor anchoring the implant to a vertebral body, such as the plate member50. As shown, the proximal end 20 p can also tend to have rounded edges.The proximal end 20 p can also include one or more features that enablethe implant to be mated to an insertion instrument. An example of such afeature is threaded bore 32 (FIG. 2D).

The surfaces 22, 24, 26, and 28 that define the external surface of thecage member 20 are sized and shaped in a manner that optimizes theplacement and fixation of implant 10 between vertebral bodies in thecervical region of the spine, and particularly when the implant ispositioned within the spine through lateral or posterior-lateral access.In the illustrated embodiment the surfaces 22, 24, 26, and 28 areconfigured to be complementary to the shape of the vertebral bodies atthe site of implantation. For example, the anterior wall 26 is curvedand is configured to be disposed at or proximate to an anterior portionof the vertebral body, while the posterior wall 28 is also curved and isconfigured to be disposed at or proximate to a posterior portion of thevertebral body. As illustrated, a curve CAW of the anterior wall 26 isgenerally convex (FIG. 2B) while a curve C_(PW) of the posterior wall 28is generally concave (FIG. 2A). Radii R_(CAW), R_(CPW) of the curvesC_(AW), C_(PW) can vary depending on the size of the implant. Generally,however, the radii R_(CAW), R_(CPW) are substantially the same and canbe in the range of about 7 millimeters to about 25 millimeters. In oneembodiment the radii R_(CAW), R_(CPW) can be about 10 millimeters.

In the embodiment illustrated in FIGS. 2A-2F, the superior and inferiorsurfaces 22 and 24 are substantially linear. However, in otherembodiments, for example the embodiment illustrated in FIG. 3A, animplant can have superior and inferior surfaces that are generallycurved. The implant 10′ shown in FIG. 3A can include a cage member 20′with an external surface that includes a superior surface 22′, aninferior surface 24′, and an anterior wall 26′ that are each generallycurved. The external surface can also include a posterior wall (notshown), which can also be generally curved. Similar to what is describedin FIGS. 2A-2F, a curve C_(AW)′ of the anterior wall 26′ is generallyconvex. Further, a curve C_(S)′ of the superior surface 22′ is generallyconcave while a curve C_(I)′ of the inferior surface 24′ is generallyconvex. The radii R_(CS)′, R_(CI)′ of the curves C_(S)′, C_(I)′ can varydepending on the size of the implant, and can be in the range of about10 millimeters to about 30 millimeters. In one embodiment the radiiR_(CS)′, R_(CI)′ can be about 18 millimeters. While in some instancesthe radii R_(CS)′, R_(CI)′ can be substantially the same, in theillustrated embodiment the radii R_(CS)′, R_(CI)′ are different, withthe inferior surface having a greater degree of curvature than thesuperior surface. When the radius R_(CI)′ of the inferior surface 24′ isgreater than the radius R_(CS)′ of the superior surface 22′, as shown inFIG. 3A, the cage member 20′ has an asymmetrically-curved, bullet-shapeddistal end 20 d′ that can be described as having a generally banana-likeor canoe-like shape.

The external surface of the implant 10, 10′ may include surface featuresthat prevent migration and assist in maintaining a location of thespinal implant. For example, in the illustrated embodiments the superiorand inferior surfaces 22, 22′ and 24, 24′ include a plurality of ridges34, 34′. Ridges 34, 34′ can take a variety of forms, as one skilled inthe art will appreciate. However, in one embodiment the ridges can be ofa triangular cross section with the apex at a distal position and aone-way directional slant as shown for example in FIGS. 2C and 2E. Thedirectional slant allows insertion of the implant but resists itsremoval. Other surface features known to those skilled in the art canalso be provided without departing from the spirit of the invention.

The external surface of the implant 10, 10′ may also include a pluralityof relief slits or openings 30, 30′ to permit access to an internalvolume within the implant. As those skilled in the art will appreciate,the internal volume may be packed with bone graft and/or bonegrowth-promoting materials to enhance and expedite integration of theimplant into a subject's body. While in the illustrated embodiment ofFIGS. 2A-2F each of the superior surface 22, inferior surface 24,anterior wall 26, and posterior wall 28 including openings 30, in otherembodiments only some of the surfaces or walls may include anopening(s), or even none of the surfaces or walls may include openings.Similarly, more than one opening can be formed on one or more sides ofthe external surface.

The presence of a plate member 50 part of the implant 10 is optional.FIG. 3A illustrates an embodiment in which the implant 10′ of FIG. 3Adoes not include a plate member. Although a plate member can assist insecuring the implant at a desired location between vertebral bodies, theshape of the implant itself can provide sufficiently secure placement ofthe implant. For example, the banana-like shape and asymmetrical curveof the implant 10′ enables stable placement of the implant 10′ withoutthe need for a plate member.

FIGS. 2A-2F illustrate an implant 10 that does include a plate member 50disposed in proximity to the proximal end 20 p of the cage member 20.While in the illustrated embodiment the plate member 50 is integrallyformed with the proximal end 20 p, it can be appended to the proximalend 20 p in other ways known to those having skill in the art. By way ofnon-limiting examples, a plate member can be slidingly coupled to a cagemember or removably and replaceably coupled to a cage member.

The plate member 50 generally extends in a direction that is opposite tothat of the elongate direction of the cage member 20. As shown in FIG.2A, while the cage member 20 extends along a long axis L₁, the platemember 50 extends in a long axis L₂ in a direction that is generallyperpendicular to the direction of the longitudinal axis L₁. The platemember 50 can also be asymmetric with respect to the long axis L₁. Inthe illustrated embodiment, the plate member 50 is entirely on one sideof the long axis L₁. In one embodiment the orientation of the platemember 50 and the cage member 20 is such that when the cage member isparallel to the transverse axis of a subject's body, the plate member isnot parallel to the sagittal plane. Rather, the plate member isanteriorly offset such that it is angled with respect to the sagittalplane. Such a construction enables the plate member to be mounted to ananterior portion of the lateral wall of a vertebral body. As a result ofthe plate member 50 being biased towards an anterior side of the spinalimplant 10, a midpoint M of the plate member 50 is disposed anterior tothe long axis L₁ of the cage member 20 as shown in FIG. 2F. Accordingly,an angle A₂ formed by orientation of the plate member 50 and theorientation of the cage member 20 (illustrated by the long axis L₁ ofthe cage member 20 and the short axis L₁ of the plate member 50) can beless than 90 degrees (FIG. 2F), and is generally in the range of about35 to about 80 degrees. In one embodiment the angle A₂ can be about 47degrees. A configuration in which the midpoint M of the plate member 50is disposed anterior to the long axis L₁ of the cage member 20 can allowthe plate member 50 to mount on a proximal lateral wall of the spine,anterior to the Carotid artery, within the C3 to C7 vertebrae range ofthe spine.

The plate member 50 is also curved along its short axis Ls, as shown inFIG. 2A, to complement the shape of the lateral walls of the vertebraeupon which the plate member will mount. As shown in FIG. 2A, an internalsurface 51 of the plate member 50 has a concave shape. Although a radiusR_(CP) of a curve C_(P) of the plate member 50 can vary, it is generallyin the range of about 10 millimeters to about 30 millimeters. In oneembodiment the radius R_(CP) is about 15 millimeters.

One skilled in the art will appreciate that the plate member 50 can havea variety of shapes and sizes. In the illustrated embodiment the platemember 50 is generally rectangular and it extends in both the superiorand inferior directions of the cage member 20. Alternatively, it canextend in a single direction such that it mates to only one of the twoadjacent vertebral bodies. The plate member 50 can include one or moremating features to assist in mating the plate member 50 to vertebrae. Asshown, the mating features can include a first bore 56 in a first wing52 of the plate member 50 and a second bore 58 in a second wing 54 ofthe plate member 50. Anchor members, such as screws complementary to thebores 56, 58, can then be used to secure the plate member 50, and thusthe spinal implant 10.

Mating features configured to be engaged by an insertion instrument canalso be provided as part of the plate member. In the illustratedembodiment a threaded bore 32 is provided as such a mating feature. Asshown, the threaded bore 32 of the plate member 50 can be engaged by aninstallation instrument (not shown) to assist in the insertion of theimplant 10. The illustrated embodiment also includes further featuresfor receiving insertion instruments. For example, a receiving groove 62is provided that provides an indentation between the first and secondwings 52 and 54 of the plate member 50. As illustrated, the receivinggroove 62 includes a chamfer 64 that can be formed to be complementaryto a shape of an insertion instrument.

In some embodiments the plate member can include one or moreanti-migration features. For example, one or more spikes, ridges, orother bone-engaging features can be disposed on the internal surface 51of the plate member 50. These features can be configured to engage anadjacent vertebral body to assist in maintaining the plate, and therebythe implant, at a desired location.

FIG. 3B illustrates another embodiment of a spinal implant 10″ havingboth a cage member 20″ and a plate member 50″. The external surface ofthe cage member 20″ is generally similar to the cage members 20 and 20′,although as shown the superior surface 22″ includes more than one reliefslit or opening 30″ formed therein. In one embodiment, the plate member50″ is asymmetric with respect to a long axis L₁″ of the cage member20″. That is, the plate member 50″ is not equally sized and shaped onboth sides of the long axis L₁″. A curve C_(P)″ of the external surfaceof the plate member changes as the curve C_(P)″ moves from the posteriorwall 28″ to the anterior wall 26″. In one embodiment a radius R_(CP)″ ofcurvature of the curve C_(P)″ can be approximately in the range of about5 millimeters to about 30 millimeters proximate to the posterior wall28″ and approximately in the range of about 5 millimeters to about 45millimeters proximate to the anterior wall 26″. In one embodiment theradius R_(CP)″ is about 5 millimeters proximate to the posterior wall28″ and about 20 millimeters proximate to the anterior wall 26″.

In the illustrated embodiment, the midpoint M″ of the plate member 50″is approximately aligned with the long axis L₁″ of the cage member 20″,although it can be offset anteriorly as described herein. Successivetangent lines, as shown lines T₁″ and T₂″, are asymmetric to the longaxis L₁″. For example, as a tangent line of the plate member 50″ movessuccessively from the posterior wall 28″ to the anterior wall 26″, anangle A_(T)″ formed by the tangent line and the long axis L₁″ decreases.In one embodiment the angle A_(T)″ decreases from an initial point(i.e., posterior most) adjacent to the posterior wall 28″ in which theangle A_(T)″ is in the range of about 80 degrees to about 95 degrees, toa point adjacent to the anterior wall 26″ in which the angle A_(T)″ isin the range of about 35 degrees to about 50 degrees. In the illustratedembodiment the angle A_(T)″ for the tangent line T₁″ is about 90 degreesand the angle A_(T)″ for the tangent line T₂″ is about 45 degrees.

Although the spinal implant 10 is described as having two components, acage member 20 and a plate member 50, each being generally rectangularin shape and having particular curvatures that can be advantageous incertain instances, a variety of other shapes and curves can also be usedin such cervical spine techniques without departing from the spirit ofthe invention. Accordingly, although the cage member is described asbeing of a generally rectangular shape and having walls and surfacesthat are convex or concave, any walls and surfaces of the cage membercan be virtually any shape, including generally flat, convex, orconcave. Likewise, the cage member can take the form of a variety ofother shapes. Similarly, plate members can have a variety ofconfigurations. Non-limiting examples of configurations of plate membersthat can be used in accordance with the present invention are providedin FIGS. 4A-4F.

As shown in FIGS. 4A and 4B, some embodiments of implants 10′″, 10″″ caninclude bend zones 53′″, 53″″ associated with the connection betweencage and plate members 20′″, 20″″ and 50′″, 50″″. The bend zones 53′″,53″″ provide a level of flexibility or adjustability between the platemember 50′″, 50″″ and the cage member 20′″, 20″″ and can allow the platemember 50′″, 50″″ to more accurately conform to an anatomy of avertebral body, as shown in FIG. 4A with respect to the vertebral bodyV′″. An angle A₃ formed by a proximal end 20 p′″ of the cage member 20′″and a tangent T_(P)′″ of the plate member can be in the range of about10 degrees to about 50 degrees. In one embodiment the angle A₃ is in therange of about 30 degrees to about 45 degrees. As shown in FIG. 4B, bendzones 55″″ can also be formed within the plate member 50″″ itself,providing further flexibility and conformity to a desired surgicallocation.

As discussed above, the plate member can include a variety of differentshapes and sizes. Non-limiting examples of plate member shapes are shownin FIGS. 4C-4F. A plate member 1650 of an implant 1610 shown in FIG. 4Cis substantially flat and mates to a cage member 1620 by way of atriangular coupling portion 1649. A plate member 1650′ of an implant1610′ in FIG. 4D is substantially V-shaped and is mounted to a cagemember 1620′ by way of a polygonal coupling portion 1649′. A platemember 1650″ of an implant 1610″ shown in FIG. 4E is substantiallyU-shaped and is mounted to a cage member 1620″ by way of a polygonalcoupling portion 1649″. A plate member 1650′″ of an implant 1610′″ shownin FIG. 4F is substantially curved and is mounted to a cage member1620′″ by a flexible coupling portion 1649′″. Any or all of theseembodiments can include bend zones, like the bend zones 1653′″ of theimplant 1610′″ of FIG. 4F, and can include characteristics and featuresof the other implants described herein.

A proximal end of a plate member can also have a variety of shapes inaddition to the generally rectangular shape illustrated in FIGS. 2A-2F.In the embodiment shown in FIG. 5A, for example, a proximal end 1750 pof a plate member 1750 of an implant 1710 can be generally triangular.As shown, a superior end 1750 s of the plate member 1750 includes onebore 1756 while an inferior end 1750 i includes two bores 1758.Anchoring elements 1770 that are configured to be disposed in the bore1756, 1758, can engage adjacent vertebrae V_(A) and V_(B). Inembodiments in which more than one bore is associated with the samevertebral body, such as the bores 1758, the bores 1758 can be configuredin a manner such that the anchoring elements 1770 disposed therein arenon-parallel. Further, multiple points of fixation can be achieved by asingle anchoring element. For example, as shown in FIG. 5B, an anchoringelement 1870 can cause bilateral fixation by being fixed through a platemember 1850 at both a proximal end V_(P) of a vertebral body V, i.e.,the first cortex, and a distal end V_(D) of a vertebral body V, i.e.,the cortical wall, the fixation element 1870 terminating past thecortical wall of the same vertebral body V.

One skilled in the art will appreciate that the implant can be made fromany number of biologically-compatible materials used to form spinalimplants, including materials that are partially or fully bioresorbable.Exemplary materials include titanium, titanium alloys, titanium mesh,polyether ether ketone (PEEK), reinforced PEEK, and Nitinol®.

In a method of implanting the lateral anterior fusion cages illustratedand described herein, an incision or delivery aperture in the range ofapproximately 25 millimeters to approximately 35 millimeters can beformed in an area near the cervical region of the spine. In an exemplaryembodiment, the incision is formed at a location that is lateral orposterior-lateral of a subject, as illustrated in FIG. 1. The devicesand methods allow for spinal implants to be implanted in a subject Hfrom a lateral point of access LP such that the point of insertion issubstantially perpendicular to the sagittal plane S. Alternatively, thepoint of insertion can be posterior of the lateral point of access LP,for example up to about 45 degrees posterior to the lateral point ofaccess LP. In some embodiments, the point of insertion can be anteriorto a lateral point of access. For example, a surgeon can approachanterior to the Carotid artery and the Jugular vein and can retract asheath used to insert the implant posterior following insertion.

After the incision is formed, and after any desired or necessarypreparation of the space between the vertebrae, an implant can beinserted through the incision and to a desired implant location.Alternatively, an access port can be inserted into the incision to forman insertion channel and the implant can be inserted therethrough andplaced at a desired implant location. In one exemplary embodiment thedesired implant location is in the cervical region of the spine,preferably between any two of the vertebrae in the C3 through C7 region,and more particularly is configured to be disposed between the C4 and C5vertebrae. The distal end of the cage member can first be inserted intothe space between the desired vertebrae, and then the implant can berotated to the desired implant location. In one exemplary embodiment thecage member can fill about one-third to about two-thirds of thefootprint of a vertebral body.

As explained above, the implant is shaped to match the contours of thedesired implant location. Accordingly, in one exemplary embodiment thesuperior and inferior surfaces 22, 22′ and 24, 24′ are configured tosubstantially match the anatomy of a central to posterior portion ofadjacent vertebral bodies such that the implant 10, 10′ can be rotatedto and then implanted at a central to posterior portion of the adjacentvertebral bodies. This implant location can be desirable in order tosuccessfully navigate the uncinate processes. In other embodiments theanterior wall 26, 26′ of the cage member 20, 20′ can be substantiallyaligned with the curve of the anterior portions of the vertebrae. Instill other embodiments the implant 10, 10′ can be implanted at an anglewith respect to a spine. Thus, while the embodiment illustrated in FIG.3A shows the implant 10′ at zero degrees (i.e., aligned with thetransverse axis of the subject's body), in other embodiments the implantcan be placed at an angle with respect to the transverse axis at a rangebetween about 1 degree and about 89 degrees, and more preferably betweenabout 30 degrees and about 45 degrees. The angle can be created duringthe act of inserting the implant through the incision, or any timethereafter, including at the site of the vertebral bodies.

In embodiments that include a plate member, such as the implant 10, theplate member 50 can be positioned so that it is adjacent to thevertebrae, closer to the anterior portion of the spine. The plate member50 can then be fixed to one or both of the vertebrae such that themidpoint M of the plate member 50 is disposed anterior to the long axisL₁ of the cage member 20. Bone graft or bone growth-promoting materialcan be incorporated into the cage member before, during, or afterinsertion is complete.

Intra-Facet Fusion Screws and Staples

Another spinal implant for use in treatment of the cervical region ofthe spine, referred to herein as an intra-facet fusion screw, isillustrated in FIGS. 6A-12B. Another implant, referred to herein as anintra-facet staple, is illustrated in FIGS. 13A and 13B. The screws andstaples can be used by themselves as spinal implants, and are designedto be implanted directly between two facets between the diarthrodialsurfaces of the facet joint.

In one embodiment of an intra-facet screw 110, illustrated in FIGS.6A-6C, the screw 110 can include a body portion 120 and a head portion150. As illustrated, the body portion 120 can be generally cylindrical,hollow, and can include one or more relief slits or openings 130 in itssurface to allow bone graft or bone growth-promoting materials to bedisposed therein. In the illustrated embodiment there are four elongateopenings 130, although the number, size, and shape of the openings canvary across different embodiments, as will be appreciated by a personskilled in the art. A bore 132 extending through the body portion 120can be any shape, and the shape need not match the shape of the bodyportion 120. However, in the illustrated embodiment the bore 132 isgenerally cylindrical and extends from the head portion 150 all the waythrough a distal end 120 d of the body portion 120.

The body portion 120 can have threads 134 formed on an external surface,allowing the screw 110 to be more easily placed between opposed superiorand inferior surfaces of the facet joint. Further, the threads 134 canalso provide additional grooves on which bone graft and bonegrowth-promoting materials can be disposed. In the illustratedembodiment the distal end 120 d is tapered, which provides additionalassistance in placing the screw 110 in a desired location. The bodyportion 120 can also be configured to be expandable, which can assist inpositioning the screw 110 in a desired location and subsequently holdingthe screw 110 in place. While a person skilled in the art will recognizea number of features that can be incorporated into the screw 110 to makeit expandable, in some embodiments the relief slits or openings 130themselves can provide that capability. In other instances, anexpandable material can be used as part of the structure of the screw110.

A diameter of the head portion 150 can generally be greater than adiameter of the body portion 120. As a result, the screw 110 can bestopped at a desired location by abutting a distal surface 152 of thehead portion 150 against bone near the desired location. A bore 160 ofthe head portion 150 that corresponds with the bore 132 of the bodyportion 120 can also include additional features to assist in matingwith insertion instruments. As shown, a hex-screw head having a seriesof six grooves 162 is provided in the bore of the head portion to allowa similarly-shaped insertion instrument to engage the screw 110 forimplantation. Although the head portion 150 is illustrated as beinggenerally cylindrical or spherical, in some embodiments the head portioncan be configured to have a shape that is complementary to a shape ofthe facet against which it is designed to rest.

One skilled in the art will appreciate that the implant can be made fromany number of biologically-compatible materials used to form spinalimplants, including materials that are partially or fully bioresorbable.Exemplary materials include titanium, titanium alloys, polyether etherketone (PEEK), reinforced PEEK, and Nitinol®. Further, in someembodiments different portions of the screw may be made of differentmaterials. For example, the head portion may be made from a differentmaterial than the body portion or a distal end of the body portion maybe made from a different, possibly harder material, than the remainderof the body portion.

While the screws can have a number of shapes and sizes, in someembodiments a diameter of the body portion 120 is approximately in therange of about 5 millimeters to about 19 millimeters while a diameter ofthe head portion 150 is approximately in the range of about 7millimeters to about 22 millimeters. The size of the diameter of thebody portion 120 and the size of the diameter of the head portion 150can depend on each other, and in one embodiment the diameter of the bodyportion is approximately in the range of about 5 millimeters to about 6millimeters and the diameter of the head portion is approximately in therange of about 7 millimeters to about 8 millimeters. Further, in someembodiments, a length of the body portion 120 can be approximately inthe range of about 7 millimeters to about 30 millimeters. In oneembodiment the length of the body portion 120 is approximately in therange of about 10 millimeters to about 12 millimeters. Other shapes anddesigns can be used depending on the location that the screws 110 areintended to be implanted. Still further, while the illustratedembodiment shows the screw 110 as a unitary component, in otherembodiments the body portion 120 can be disengaged from the head portion150 or the body portion 120 can be broken apart into two or moresections.

A number of other embodiments of facet screws 210, 310, 410, and 510 arealso provided in FIGS. 7-10. The screw 210 of FIG. 7 includes a bodyportion 220 having a plurality of threads 234 disposed thereon, a bore232 extending therethrough, and a plurality of elongate relief slits oropenings 230 formed therein. A head portion 250 is integrally formedwith the body portion 220. The screw 210 of FIG. 7 differs from thescrew 110 of FIGS. 6A-6C because a distal end 220 d of the body portion210 of FIG. 7 is not tapered.

FIG. 8 illustrates another embodiment of an intra-facet screw 310. Thescrew 310 includes a body portion 320 having a bore 332 extendingtherethrough and a head portion 350. A diameter of the head portion 350can be larger than a diameter of the body portion 320. However, asillustrated, the difference between the diameters of the body and headportions 320 and 350 in the screw 310 is not as pronounced as inembodiments shown in FIGS. 6A-6C and 7. Further, unlike the embodimentsof FIGS. 6A-6C and 7, the body portion 320 is not threaded. Instead, aplurality of edges 334, 336 is formed on the body portion 320. Some ofthe edges 334 extend along most of the length of the body portion 320,while other edges 336 are formed on either end of elongate openings 330in the body portion 320. Like the other embodiments, any number ofrelief slits or openings 330 can be formed in the body portion 320.

As illustrated, a distal end 320 d of the body portion 320 is tapered,and although in the illustrated embodiment the edges 334, 336 do notextend onto the tapered distal end 320 d, in other embodiments the edges334, 336 can extend onto the tapered distal end 320 d. Further, aplurality of spikes 338 can be formed around a circumference of thescrew 310 such that the spikes 338 extend from the head portion 350 andonto the body portion 320. The spikes 338 can assist in maintaining alocation of the screw 310 as it is implanted in a desired location.

Yet another embodiment of an intra-facet screw 410 is illustrated inFIG. 9. The screw 410 of FIG. 9, which is similar to the screw in FIG.7, includes a body portion 420 having a bore 432 extending therethrough,a plurality of elongate relief slits or openings 430 formed in the bodyportion 420, a tapered distal end 420 d, and is not threaded. Further, ahead portion 450 includes a plurality of spikes 438 around acircumference of the screw 410 and that extend onto the body portion420.

Still a further embodiment of an intra-facet screw 510 is illustrated inFIG. 10. The screw 510 of FIG. 10 is more closely akin to the screws 110and 210 of FIGS. 6A-6C and 7 because the screw 510 includes a bodyportion 520 having a bore 532 extending therethrough and threads 534formed thereon, as well as a head portion 550 that has a diameter thatis significantly larger than a diameter of the body portion 520. Whilethe body portion 520 does include a plurality of relief slits orelongate openings 530 formed therein, the openings 530 do not close atthe distal end 520 d. This results in the formation of an elongate bodythat includes four fingers 540. This embodiment can provide additionalflexibility in implanting the screw 510 in a desired location becausethe distal end 520 d can be easier to manipulate in and out.

One method of using implants of the nature illustrated and describedwith respect to FIGS. 6A-10 is illustrated by FIGS. 11A and 11B. Asshown, an intra-facet screw 610 having a body portion 620 and a headportion 650 can be disposed adjacent of a desired implant location inthe cervical region of the spine. The screw 610 can be placed at adesired location in a manner similar to the methods described above forimplanting the implants of FIGS. 2A-3. Thus, for example, a lateral orposterior-lateral incision can be formed in an area near the cervicalregion of the spine and the intra-facet screw 610 can be insertedthrough to the cervical region of the spine directly, or through a portplaced in the incision. An angle of insertion can be substantiallyperpendicular to the sagittal plane of a subject, or it can be at anangle posterior to perpendicular to the sagittal plane, as shown forexample in FIG. 1.

After the intra-facet screw 610 is in the vicinity of its desiredimplantation site, it can be pushed between two adjacent facet joints,as shown facet joints F6 and F7, until a distal surface of the headportion 650 of the screw 610 is flush against a portion of the bone. Inother embodiments the screw can be inserted even further such that aproximal surface of the screw is flush with the bone or passes beyondthe surface of the bone. Bone graft or bone growth-promoting materialcan be added to the screw 610 after insertion is complete, for instancethrough a bore 632. In embodiments in which the body portion 620 isthreaded or in which there are openings formed in the body portion 620,the bone graft or bone growth-promoting material can be associated withthose portions before, during, or after implantation.

FIGS. 12A and 12B illustrate another intra-facet screw 710 disposed in acervical region of the spine. Implantation of this screw 710 can beperformed in a manner similar to the manner described with respect toFIGS. 11A and 11B. As shown, threads 734 of a body portion 720 canengage the adjacent facet joints, as shown facet joints F6 and F7, whenthe screw 710 is driven into the space between the F6 and F7 facetjoints and the screw 710 comes to rest when a head portion 750 engagesthe bone. The screw 710 includes a hex-head 762 such that a hex-shapedinsertion instrument can be used to drive the screw 710 into its desiredlocation. After the insertion instrument is removed, any areas notalready filled with bone graft or bone growth-promoting material can befilled with such a material, including a bore 732 extending through thebody portion 720, openings 730 in the body portion, and the threads 734.

FIGS. 13A and 13B illustrate another embodiment of a spinal implant 810.The implant 810 includes lateral staples 820 configured to be disposedbetween lamina of the spine, or adjacent structures such as the spinousprocess. As shown in FIG. 13B, the staples can include anelliptically-shaped central portion 830 and engaging arms 850. Thestaples 820 can be made of a temperature-sensitive material, such asNitinol®, such that the staples can assume a desired configuration upondelivery between adjacent vertebrae. As a temperature increases, thecentral portion 830 can expand and the engaging arms 850 can close. Inone embodiment the staple 820 is delivered so that the engaging arms 850are disposed partially in adjacent lamina. As the temperature increases,the central portion 830 expands and the engaging arms move toward eachother, causing the adjacent lamina to be pulled together.

Other shapes of staples can be used. Additionally, the dimensions ofsuch staples can vary, depending on spacing between lamina that existsand the desired spacing between lamina. For example, a length of astaple from one arm to the other arm can be about 10 millimeters toabout 50 millimeters. In one embodiment it can be about 12 millimetersand in another embodiment it can be about 20 millimeters. Likewise, alength of an arm itself can vary, and can be in the range of about 6millimeters to about 20 millimeters. In one embodiment a length of onearm can be about 6 millimeters and a length of another arm can be about10 millimeters. In some embodiments the staples can be asymmetric suchthat the length of one arm is different than the length of the secondarm of the same staple, while in other embodiments the lengths of eacharm can be substantially equal. Further details about staples that canbe adapted for use as a spinal implant in view of the teachingscontained herein are found in U.S. Pat. No. 5,779,707, the contents ofwhich is incorporated by reference in its entirety.

A number of methods can be used to implant staples of the naturedescribed with respect to FIGS. 13A and 13B. For example, in embodimentsin which the staples are temperature-controlled, the staples can firstbe brought to a temperature at which its arms are open for implantation.In one exemplary embodiment, the staples are kept for at least two hoursat a maximum temperature of about 0° F. (−18° C.). Following theformation of an incision to implant the staples, using techniquesdescribed herein for instance, the implantation site can be prepared toreceive the staples. This can include using any number of guides,drills, and wires, among other instruments, to prepare vertebral bodiesfor receiving the staples. For example, temporary pins can be used toprevent displacement of structures at or adjacent to the implantationsite. Likewise, guides can be used to place the vertebral bodies at anideal location for receiving the staples.

Once the implantation site is properly prepared, one of the staples canbe inserted to the surgical location and implanted such that a first armof the staple is driven into a portion of a first vertebral body and asecond arm of the staple is driven into a portion of a second vertebralbody. A surgical stapler, impactor, such as a Memory arthrodesisimpactor, or any other known tool for applying staples, can be used toimplant the staples. Further, any number of instruments can be used toassist with the insertion of the staples, such as guides and pins.

Once the staple is located in its desired location, any instruments usedto assist with the preparation of the implantation site or theimplantation of the staple can be removed. Further, the arms can beactuated toward a central portion of the staple to close the arms. Thiscan result naturally from the temperature of the surgical location,which is higher than the starting temperature of the staples, or asurgeon can control the temperature at the surgical site to assist inthe actuation of the arms. Actuation of the arms results in thevertebral bodies in which the arms are engaged being drawn toward eachother. Other staples can be implanted in a similar manner.

Although in the embodiment illustrated in FIG. 13A the staples 810 areimplanted in adjacent vertebral bodies, in other embodiments the staplescan span across two or more vertebral bodies. Further, additionalmethods for operating staples of the nature disclosed herein can befound in the Memory Staple Surgical Technique, a publication distributedby DePuy Spine, Inc., a Johnson & Johnson company, the contents of whichis incorporated by reference in its entirety. Although the techniquesdescribed in that publication are generally directed to implantation ina subject's foot, a person skilled in the art would be able to adaptthose techniques for use in vertebral bodies based on the disclosurescontained herein.

Lateral Posterior Fusion

Other implants for use in a cervical region of the spine can include oneor more spinal fixation elements, such as rod members, capable ofextending across a plurality of vertebral bodies. A person skilled inthe art will recognize that the use of spinal stabilization members inthe cervical region of the spine can be helpful in treating a variety ofabnormalities. The spinal stabilization members of the presentinvention, which are illustrated in FIGS. 14A-21B, are particularlyuseful because they provide the mobility and flexibility of using a rodwhile also providing the benefit of having multiple fixation points.Spinal fixation elements disclosed herein avoid some of the drawbacksassociated with previously known spinal fixation elements, which havelimited placement flexibility due to the need to affix them to the spinewith separate plate members or other attachment means. The use offixation points that are formed on the rod itself dramatically increasesthe number of points at which the rod members can be fixed. Byincreasing the number of fixation points at which the rod member can befixed, the spinal fixation elements become substantially more versatilefor use in the cervical region of the spine. The number of possibleimplant locations increases, and thus, the number of possible roddesigns increases.

One exemplary embodiment of a spinal implant 910 that includes a rodmember 920 for use in treating the cervical region of the spine isillustrated in FIGS. 14A and 14B. FIG. 14A illustrates a single,elongate rod member 920, while FIG. 14B illustrates two rod members 920implanted in a cervical region of a spine. Anchor members 970, such asbone screws, can be used to secure the rod members 920 at desiredlocations in one or more of the vertebrae.

In the exemplary embodiment illustrated in FIG. 14A, the rod member 920is generally elongate between its proximal and distal ends 920 p, 920 d.While the rod member 920 can be substantially straight, in theillustrated embodiment the rod member 920 is curved at least in oneplane. Those skilled in the art will appreciate that the curve of therod member can take any shape needed to address a patient's condition.In instances in which a patient suffers from lordosis or anothercondition, a curve can be substantially similar to a curve of the spinethat results from lordosis or another condition. In some embodiments, aplurality of shorter rod members can be used to allow for a profile of aspine to be biomechanically matched.

Alternatively, a longer rod member can be designed to biomechanicallymatch a spine profile. A radius RR of a curve CR of the rod member 920can be in the range of about 0 millimeters to about 500 millimeters, andin one embodiment the radius RR is about 4 millimeters. A person skilledin the art will recognize that the radius of the curve of a spinalfixation element may change throughout its distribution because thecurve can be asymmetric.

In embodiments in which the rod member 920 includes a curve, the curvecan be pre-determined. Alternatively, the rod member 920 can includesome flexibility or malleability to allow it to be shaped as desired bya surgeon at the time of a surgical procedure. In other instances therod member 920 can be fully bendable so it can be formed into anydesired shapes across its length. In one embodiment the rod member 920is substantially S-shaped, while in another embodiment it issubstantially Z-shaped. Any number of shapes can be achieved by the rodmember 920. Likewise, the rod member 920 can have any size. It can besized for use in the cervical region of the spine, and more particularlyto extend between any length between the C1 and C7 vertebrae. As shownin FIG. 14B, the rod member 920 extends between the C3 and the C7vertebrae. The length of the rod member can be in the range of about 20millimeters to about 250 millimeters, and in one embodiment can be about35 millimeters. Likewise, the rod member can have a variety ofthicknesses. For example, the rod member can have a thickness in therange of about 3 millimeters to about 20 millimeters, or in the range ofabout 3 millimeters to about 5.5 millimeters, and in one embodiment canbe about 4 millimeters. The rod member can also have a variety of crosssectional shapes, including circular, ovoid, square, rectangular,triangular, etc.

The rod member 920 can include features configured to assist with itsimplantation at a desired surgical location. In the illustratedembodiment the distal end 920 d includes a V-shaped notch 932, which iscomplementary to a distal end of an insertion instrument such that theinsertion instrument can engage the rod member 920 at the V-shaped notch932 to direct the rod member 920 to a desired location. Although in theillustrated embodiment the notch 932 is V-shaped, any number of shapesand configurations can be used to assist in mating an insertioninstrument with the rod member 920. Likewise, a person skilled in theart will recognize other ways by which the notch 932 can be used toinsert the rod member 920 to a desired surgical location.

The rod member 920 can also include one or more mounting eyelets 950,951. As shown, the rod member 920 includes two mounting eyelets—thefirst mounting eyelet 950 is disposed in proximity to the distal end 920d and the second mounting eyelet 951 is at the proximal end 920 p. Theeyelets 950, 951 can be located anywhere along a length of the rodmember 920. Thus, in some embodiments an eyelet can be located at eachof the proximal and distal ends 920 p, 920 d, while in other embodimentsan eyelet can be located in proximity to a distal end 920 d and a secondeyelet can be located in proximity to a proximal end 920 p, but neitherbeing at a terminal end of the rod member 920. Eyelets can even belocated centrally along a length of the rod member 920. In someembodiments, eyelets can be slidably coupled to the rod member such thatthe location of the eyelets can be moved to desired locations at asurgical site.

The mounting eyelets 950, 951 can either be in-line with a longitudinalaxis L_(R) of the rod member 920 or offset from the longitudinal axisL_(R). For example, FIGS. 14A and 14B illustrate that the secondmounting eyelet 951 is approximately in-line with the longitudinal axisL_(R), while the first mounting eyelet 950 is offset from thelongitudinal axis L_(R). More particularly, a central axis C₁ of thesecond mounting eyelet 951 intersects the longitudinal axis L_(R) whilea central axis C₀ of the first mounting eyelet 950 is offset from thelongitudinal axis L_(R). Either or both of the eyelets 950, 951 can beselectively located approximately in-line with the longitudinal axisL_(R) or offset from the longitudinal axis L_(R).

Likewise, any number of eyelets can be used in conjunction with theelongate rod member 920 in any number of configurations with respect tothe eyelets being approximately in-line or offset from the longitudinalaxis of the rod member. In instances in which the rod member includes adesired shape, such as an S-shape or a Z-shape, each eyelet can serve asa vertex of the desired shape. Thus, if a rod member 920′ issubstantially S-shaped, as illustrated in FIG. 15, a first and thirdmounting eyelet 950′, 953′ can be disposed on one side of a central axisCA′ that bisects the rod member 920′ and a second and fourth mountingeyelet 951′, 955′ can be disposed on the other side of the central axisCA′. As shown, the first and second mounting eyelets 950′, 951′ areoffset with respect to the rod member 920′, while the third and fourthmounting eyelets 953′, 955′ are substantially in-line with respect tothe rod member 920′. Further, the first and second mounting eyelets950′, 951′ are in proximity to distal and proximal ends 920 d′, 920 p′,respectively, while the third and fourth mounting eyelets 953′, 955′ aredisposed approximately at vertices A and B, respectively. As is the casewith all of the embodiments in the present disclosure, othercombinations of locations of eyelets can also be used with the rodmember 920′.

The eyelets 950, 951 can be configured to receive a variety of anchoringmembers (e.g., hooks, bolts, wires, screws, anchors, etc.), but as shownthe eyelets 950, 951 each include a circular bore 950 b, 951 b so thatanchoring members 970, such as screws, can be disposed therethrough. Inone embodiment the mounting eyelets 950, 951 can be configured such thatanchoring members disposed therein need not be oriented to extendparallel to each other. That is, the eyelets can be designed to allowfor polyaxial movement of the anchor members engaged therein. By way ofexample, an internal surface of the eyelets can be substantiallyspherical so as to correspond with a spherical head (not shown) of theanchor element such that the head can rotate relative to the eyelet asin a ball-in-socket joint.

Alternative spinal fixation elements are illustrated in FIGS. 15-21B.FIG. 15, as previously discussed, illustrates a rod member 920′ havingan S-shape having at least one vertex and having eyelets 950′, 951′,953′, and 955′ disposed on either side of the central axis CA′ thatbisects the implant 910′.

FIGS. 16A and 16B illustrate an embodiment of a spinal fixation element1010 in which a rod member 1020 is used in conjunction with a connector1080 and an anchor member 1090. As shown, the rod member 1020 includesan offset mounting eyelet 1050 in proximity to a distal end 1020 d ofthe rod member 1020, an in-line mounting eyelet 1051 at a proximal end1020 p of the rod member 1020, and a third mounting eyelet 1053 disposedbetween the eyelets 1050 and 1051. As shown, the third eyelet 1053 is anin-line mounting eyelet that is slidably mounted upon the rod member1020. Further, the third eyelet 1053 is configured to couple to theanchor member 1090 that is disposed adjacent to and offset from the rodmember 1020 by way of the connector 1080, enabling the rod member 1020to be secured to the spine at a location intermediate the eyelets 1050,1051. This can be useful, for example, when part of a vertebra has beenremoved or lacks sufficient strength to receive an anchor member.

As shown in FIG. 16A, the connector 1080 extends between a connectorhousing 1092 of the anchor member 1090 and the eyelet 1053. Theconnector 1080 can be secured within the housing 1092 by a set screw1094 and is secured to the third eyelet 1053 and the rod member 1020 bya set screw 1096. In use, the anchor member 1090 can secure theconnector housing 1092 to a sound portion of the vertebra and, whenproperly positioned, the eyelet 1053 can be secured in its desiredlocation using the set screw 1096. A person skilled in the art willrecognize a variety of ways in which the slidable third eyelet 1053 canbe secured to a vertebra offset from the rod member 1020 by way of theconnector 1080 and anchor member 1090.

As more clearly shown in FIG. 16B, in some embodiments one or more ofthe mounting eyelets 1051 can include a pivoting or swivel feature. Sucha feature provides additional flexibility in achieving a desiredlocation for the rod member 1020. A screw 1070 can be selectivelyloosened to allow the rod member 1020 to move or swing to a desiredlocation, and then the screw 1070 can be selectively tightened to engagethe rod member 1020 and fix its location. Pivoting or swivel features ofthis nature can be incorporated to any of the mounting eyelets disclosedherein, and at any location across a length of the rod members.

FIGS. 17A and 17B illustrate an implant 1110 in the form of a spinalfixation element having a telescoping feature, thereby allowing a lengthof a rod member 1120 to be selectively adjusted. As illustrated, a firstsegment 1119 of the rod member 1120 can have a bore with an internaldiameter that is larger than an outer diameter of a second segment 1121.As a result, the first segment 1119 can receive the second segment 1121,enabling the first and second segments 1119, 1121 to slide with respectto each other such that the length between first and second mountingeyelets 1150, 1151, and thus the distance between distal and proximalends 1120 d, 1120 p of the rod member 1120, can be adjusted. While anynumber of mechanisms can be used to adjust and subsequently fix thelength of the rod member 1120, as shown the first segment 1119 iscoupled to first mounting eyelet 1150 by way of a threaded portion 1123.The first segment 1119 can be rotated around the threaded portion 1123to form different lengths of the rod member 1120. Once a desired lengthis reached, the location of the first segment 1119 can be fixed by alocking nut 1227 disposed on the threaded portion 1123 between the firstsegment 1119 and the first mounting eyelet 1150. The first segment 1119can be selectively unlocked with respect to the threaded portion 1123and the second segment 1121 and subsequently adjusted as desired. Othermechanisms for locking a location of at least one of the two segments1119, 1121 can also be used. As also shown in the illustratedembodiment, the anchor members 1170 disposed in the first and secondmounting eyelets 1150, 1151 may extend at different angles due to thepolyaxial seating of the anchor members within the eyelets 1150, 1151.

Another embodiment of a telescoping spinal fixation element implant 1210that includes a rod member 1220 having an adjustable length is shown inFIGS. 18A-18C. A first mounting eyelet 1250 is secured to the spinousprocess of a first vertebra, C2, and a second mounting eyelet 1251 issecured to the spinous process of a second vertebra, C7. As shown inFIG. 18B, each of the two mounting eyelets 1250 and 1251 is secured tothe respective C2 and C7 vertebrae by way of brackets 1255, 1257 androds 1259, 1261. The brackets 1255, 1257 can be disposed around thespinous processes and the rods 1259, 1261 can be coupled to the brackets1255, 1257 and eyelets 1250, 1251, passing through the spinous processesof the C2 and C7 vertebrae. One or more anchor members 1270 can beinserted proximate to the mounting eyelets 1250, 1251 to further securethe location of the eyelets 1250, 1251 with respect to the spine.

The rod member 1220 includes two separate segments 1219, 1221 disposedbetween the first and second eyelets 1250, 1251 and an adjustmentmechanism 1265 is provided between the two segments 1219, 1221. Asillustrated, the adjustment mechanism 1265 includes a locking memberhaving a housing 1267. Threaded ends 1217, 1223 of each of the twosegments 1219, 1221 are coupled to opposite ends of the housing 1267,and a portion of the threaded ends 1217, 1223 can be disposed within thehollow interior of the housing 1267. Locking nuts 1227, 1229 can bedisposed around the segments 1219, 1221 on the outside of the housing1267. As will be appreciated by a person skilled in the art, the lockingnuts 1227, 1229 can be rotated to selectively lock and unlock thesegments 1219, 1221 to form a rod of a desired length.

FIG. 19 illustrates yet another embodiment of a spinal implant 1310 inwhich the spinal fixation element is a rod member 1320 that includesthree mounting eyelets 1350, 1351, and 1353. As shown, eyelet 1351 isdisposed at a proximal end 1320 p of a rod member 1320 and is configuredto be generally stationary. A bore 1351 b of the eyelet 1351 isconfigured to receive an anchor member 1370 therein, and the size of thebore 1351 b is generally complementary to a size of the anchor member1370 to be disposed therein. As shown, the eyelet 1351 is integratedwithin the rod member 1320.

Mounting eyelet 1350 is shown disposed proximate to a distal end 1320 dof the rod member 1320 and it is coupled to the rod member 1320 by wayof a coupling portion 1355 disposed around at least a portion of the rodmember 1320. The position of the coupling portion 1355 is adjustable asit can slide proximally and distally along the rod member to optimizethe point of attachment to a vertebral body. The rod member 1320 can besubstantially rigid, and it can include mating features, such as ridges1334, that allow the coupling portion 1355 to more easily grip the rodmember 1320. The diameter of a bore 1350 b of the eyelet 1350 can besubstantially larger than a diameter of an anchor member 1371 disposedtherein. This configuration allows for fine adjustment of the relativeposition of the rod member 1320 and the anchor member 1371 when theanchor member 1371 is not fully seated within the bore 1350 b. That is,the rod member 1320 can be slid in a direction toward and away frommounting eyelet 1350. When the anchor member 1371 is not fully securedin the eyelet, the anchor member 1371 can be rotated in a clockwisedirection to engage the fixation element 1371 with the bore 1350 b. Thiscauses the coupling portion 1355 to tighten around the rod member 1320,thereby locking the first mounting eyelet 1350 and the rod member 1320in place to set the new location of the rod member 1320.

Similarly, the diameter of a bore 1353 b of the mounting eyelet 1353 isalso larger than the diameter of an anchor member 1373 disposed thereinand the third mounting eyelet 1353 is coupled to the rod member 1320 byway of a coupling portion 1357 disposed around at least a portion of therod member 1320. As a result, adjustments to a location of the rodmember 1320 and the coupling portion 1357 can be achieved in a similarmanner as described with respect to the first mounting eyelet 1350.

FIGS. 20, 21A, and 21B illustrate two further embodiments of implants1410 and 1510 having differently shaped rod members 1420 and 1520. Asshown in FIG. 20, the rod member 1420 is substantially thin and flat. Insome embodiments the rod 1420 can be laminar in nature. The rod member1420 illustrated in FIG. 20 includes two mounting eyelets 1450 and 1451,the first eyelet 1450 located in proximity to a distal end 1420 d of therod member 1420 and the second eyelet 1451 located in proximity to aproximal end 1420 p of the rod member 1420. As shown, each of the twoeyelets 1450, 1451 is offset with respect to a longitudinal axis LF ofthe rod member 1420, however, in other embodiments, one or more eyeletscan be substantially in-line with the longitudinal axis L_(F). Anchormembers 1470 can be disposed in bores of the eyelets 1450, 1451.

FIGS. 21A and 21B illustrate a spinal implant 1510 having a rod member1520 that includes a plurality of bends B₁, B₂, and B₃. As shown, theanatomy of the spine in which the rod member 1520 is disposed includesthree vertebrae, C4, C5, and C6, in which the spinous process is cutaway. The rod member 1520 bends closer to these portions of thevertebrae to provide additional stability. A distal end 1520 d of therod member 1520 includes a first mounting eyelet 1550 and is mounted tothe spinous process of the C3 vertebra using an anchor member 1570. Aproximal end 1520 p of the rod member 1520 includes a second mountingeyelet 1551 and is mounted to the spinous process of the C7 vertebrausing an anchor member 1570. As shown in FIG. 21B, the eyelet 1550 isoffset with respect to a longitudinal axis L_(S) of the rod member 1520and the eyelet 1351 is substantially in-line with respect to thelongitudinal axis L_(S). As shown, a first, distal bend B₁ is providedproximate to the spinous process of the C3 vertebra, and then a second,intermediate bend B₂ is provided proximate to the C4 and C5 vertebrae. Athird, proximal bend B₃ is provided proximate to the C6 and C7 vertebraeso the rod member 1520 can bend in a superior direction and terminate atthe second eyelet 1351, proximate to the posterior portion of the C7vertebra.

Any material can be used to form the spinal fixation elements disclosedin FIGS. 14A-21B, including biologically-compatible materials used toform spinal fixation elements and partially and fully bioresorbablematerials. Examples of materials suitable for use include titanium,titanium alloys, polyether ether ketone (PEEK), and reinforced PEEK. Ininstances in which it is desirable for the rod member to have someflexibility, or even be fully bendable, materials that include a shapemetal alloy, such as Nitinol®, can be desirable. Different portions ofthe length of spinal fixation elements can be made from differentmaterials to achieve different desired results. Thus, a portion of thespinal fixation element can be made from a more flexible material whileanother portion of the spinal fixation element can be made from a morerigid material. Materials can be mixed and matched as desired.

In a method of use for implants illustrated and described with respectto FIGS. 14A-21B, an incision or delivery aperture can be formedproximate to a cervical region of the spine in a manner similar to thedescribed incision formation with respect to the implants of FIGS. 2A-3,and the implant are is prepared as needed. For example, a lateral orposterior-lateral incision can be formed in an area near the cervicalregion of the spine and a rod member 920 can be inserted through to thecervical region of the spine directly or through an access port placedin the incision. An angle of insertion can be substantiallyperpendicular to the sagittal plane of a subject, or it can be at anangle posterior to perpendicular to the sagittal plane, as shown forexample in FIG. 1. For reference purposes, unless specifically stated,the embodiment illustrated in FIG. 14B is discussed herein, although themethods can be used with respect to any of the spinal implants disclosedherein.

The rod member 920 can be inserted at a position that is lateral to orposterior-lateral to the cervical region of the spine. The rod member920 can then be positioned proximate to the cervical region of the spineat a desired location. Eyelets 950, 951 of the rod member 920 can bealigned with the vertebrae in which they will be delivered. In theillustrated embodiment, the first mounting eyelet 950 is disposedproximate to the C3 vertebra and the second mounting eyelet 951 isdisposed proximate to the C7 vertebra. Then each of the mounting eyelets950, 951 can be attached to the respective vertebrae, C3 and C7, forexample by using anchor members 970. This can be accomplished in anyorder, including simultaneously if the fixation element delivery deviceis designed in such a manner.

If desired, a second rod member 920 can also be introduced to thecervical region of the spine in the same manner. As shown in FIG. 14B,the second rod member 920 can be arranged to be substantially parallelto the first rod member 920.

In embodiments that are configured to permit segments of the rod memberto slide with respect to each other, such as the embodiments illustratedin FIGS. 17A-18C, the method can include adjusting a length of the rodmember between the first and second mounting eyelets. The lengthadjustment can occur at any time during the installation process,including before any of the eyelets are fixed to a vertebra, or afterone or more of the eyelets are fixed to respective vertebrae. Even afterthe rod member is fully fixed at its proximal and distal ends, a lengthof the rod member can be adjusted to pull vertebrae apart or push themtogether as desired. Similarly, in embodiments that are configured topermit a location of mounting eyelets and rod members to be adjustedwith respect to each other, the method can include adjusting locationsof one or more mounting eyelets and one or more rod members with respectto each other to achieve a desired configuration at the surgical site.

Likewise, a shape of the rod members can be adjusted as part of theinstallation process. While the rod members can have a pre-determinedshape, the rod members can also be either slightly flexible to allow forsome minor shape changes on-site, or they can be fully bendable to allowfor any number of shapes to be formed during a surgical procedure. Thiscan allow for rod members to be shaped consistent with a profile of thespine.

Although the implants discussed herein are generally discussed withrespect to being used in a cervical region of a spine, the implants canalso be used in other regions of the spine, such as the thoracic andlumbar regions, as well as in other skeletal structures of a subject,such as skulls, femurs, tibias, and hips. Likewise, although theimplantation technique is generally described as being a lateralapproach, the implants disclosed herein can be used in other approachesand in other locations in a subject.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. A personskilled in the art will be able to apply features disclosed in oneimplant and generally apply those features to other implants as wellbecause many of the features described herein are capable of being mixedand matched across various embodiments. All publications and referencescited herein are expressly incorporated herein by reference in theirentirety.

What is claimed is:
 1. A spinal implant, comprising: an elongate cagemember having distal and proximal ends and an external surface extendingtherebetween, the external surface being defined by a generally concavesuperior surface, a generally convex inferior surface, an anterior wall,and a posterior wall, the cage having a hollow interior and a pluralityof openings formed in the external surface; wherein the inferior surfacelocated at the distal end of the elongate cage member is biased in asuperior direction towards the superior surface located at the distalend of the elongate cage member, the bias of the inferior surface beinggreater than a bias in the superior direction of the superior surfacelocated at the distal end of the elongate cage member such that thedistal end of the elongate cage member has an asymmetrical, bulletedshape.
 2. The implant of claim 1, further comprising a plate memberintegrally formed on the cage member in proximity to the proximal end ofthe cage member, the plate member having a long axis that is generallyperpendicular to a long axis of the cage member which, when viewed fromabove the superior or inferior surface, extends from the distal end tothe proximal end at a longest dimensions therebetween, and the platemember having a curve along a short axis thereof.
 3. The implant ofclaim 2, wherein the plate member is asymmetric with respect to the longaxis of the cage member such that the plate member is disposed on ananterior side of the long axis.
 4. The implant of claim 3, wherein theplate member is oriented with respect to the cage member such that amidpoint of the plate member is disposed anterior to the long axis ofthe cage member.
 5. The implant of claim 1, wherein at least one of thesuperior and inferior surfaces of the cage member includes one or moresurface features configured to prevent migration of the implant.
 6. Theimplant of claim 1, wherein the posterior wall of the cage memberincludes a curve that is generally concave.
 7. The implant of claim 1,wherein the anterior wall of the cage member includes a curve that isgenerally convex.
 8. An elongate cage member, comprising: a distalinsertion end; a proximal anchoring end opposed to the distal insertionend; a superior surface extending between the distal insertion end andthe proximal anchoring end; an inferior surface extending between thedistal insertion end and the proximal anchoring end, the inferiorsurface being opposed to the superior surface; a curved anterior wallextending between the distal insertion end and the proximal anchoringend and the superior surface and the inferior surface; a curvedposterior wall extending between the distal insertion end and theproximal anchoring end and the superior surface and the inferiorsurface, the curved posterior wall being opposed to the curved anteriorwall, wherein a radius of curvature of a distal portion of the inferiorsurface at the distal insertion end is greater than a radius ofcurvature of a distal portion of the superior surface at the distalinsertion end, the distal portions of the inferior and superior surfacesbeing opposed to each other.
 9. The elongate cage member of claim 8,wherein a distal tip of the elongate cage member includes the distalportions of the inferior and superior surfaces and portions, distalportions of each of the curved anterior wall and the curved posteriorwall, and the distal insertion end, and wherein the distal tip comprisesan asymmetrically-curved, bullet-shaped tip.
 10. The elongate cagemember of claim 8, further comprising a plate member integrally formedon at least a portion of each of the proximal anchoring end and thecurved anterior wall, the plate member having a long axis that isgenerally perpendicular to an approximately central long axis extendingfrom the proximal anchoring end to the distal insertion end, and theplate member having a curve along a short axis thereof.
 11. The elongatecage member of claim 10, wherein the plate member is asymmetric withrespect to the approximately central long axis such that the platemember is disposed on an anterior side of the long axis.
 12. Theelongate cage member of claim 11, wherein the plate member is orientedwith respect to the proximal anchoring end such that a midpoint of theplate member is disposed anterior to the approximately central longaxis.
 13. The elongate cage member of claim 8, wherein at least one ofthe superior and inferior surfaces includes one or more surface featuresconfigured to prevent migration of the elongate cage member.
 14. Theelongate cage member of claim 8, wherein the curved posterior wall isgenerally concave.
 15. The elongate cage member of claim 8, wherein thecurved anterior wall is generally convex.
 16. The elongate cage memberof claim 8, wherein the proximal anchoring end comprises a threadedbore.
 17. The elongate cage member of claim 8, further comprising aninterior open space defined by interior surfaces of the distal insertionend, the proximal anchoring end, the curved anterior wall, and thecurved posterior wall, the interior open space extending from thesuperior surface to the inferior surface.
 18. The elongate cage memberof claim 17, further comprising one or more openings formed in at leastone of the distal insertion end, the proximal anchoring end, the curvedanterior wall, and the curved posterior wall, the one or more openingsbeing in communication with the interior open space.